I don't know if this would be useful to you - here's a non-linear smoothing function implemented with a TriggeredSoundToGlobalController.
The salient part is that the !Smoothed value is:
!Smoothed + ((!Input - !Smoothed) / !Friction)
If you set !Friction to 1 then the !Smoothed value will instantly be equal to the !Input value.
If you set !Friction to 2 then the difference between !Smoothed and !Input will halve each cycle. In other words the closer !Smoothed gets to !Input the slower it will approach.
Drag Input around and watch Smoothed react
The sound file